Context: Studies identified prevalence of vitamin A deficiency among Indian preschool-aged children. Aims: The meta-analysis was conducted on peer-reviewed articles published between 1960 and 2007. Settings and Design: Thirteen epidemiologic studies were identified from 250 potentially relevant articles. Material and methods: Studies were selected on, Firstly; a broad criterion of vitamin A deficiency among Indian preschool-aged children was developed on information provided in the WHO publication. Secondly, ‘Night Blindness (XN)’ among preschool-age children along with Corneal Xerosis associated with Bitot’s spot (X1B) was considered as positive clinical signs. Finally, in absence of universally accepted criteria of reporting of prevalence, weighted average data was considered as positive cases irrespective of criteria of diagnosis. Statistical analysis used: Median and inter-quartile range was used. Results: Wide differences in samples and primary outcome variables in these studies were observed. After adjusting for these confounding characteristics, consistent patterns of vitamin A deficiency among Indian preschool-aged children was calculated. The total number of children in this study population was 208379 [with median=1094 and IQR = 283.0 – 8978.0] and the number of children suffering from Vitamin A deficiency disorders was 12510 [with median =80 and IQR = 36.5 – 201.0]. The median prevalence was 7.0% and Inter-Quartile Range (IQR) = 3.3% – 9.3%. Though the study period varied between 1960 and 2005, the median study period was found to be 1999 [with IQR = 1981.5-2004.5]. Conclusion: Wide inter-regional variation in these studies on the prevalence was possibly because of the non-uniform adherence to the diagnostic criteria.
Keywords: Vitamin A deficiency, preschool-aged children, prevalence
Vitamin A deficiency is the single most important cause of childhood blindness in the developing countries. An estimated 2.8 million preschool-age children are at a risk of blindness from vitamin a deficiency and the health and survival of 251 million others are seriously compromised.  Vitamin A deficiency disorder spectrum has the unique distinction of being one of the most important causes of ‘Preventable blindness’ the world over, and xerophthalmia still remains a problem in the developing countries. [2 ] In India alone, 52,000 children are found to go blind every year on account of vitamin A deficiency., Studies in the recent past have shown that not only does vitamin A deficiency causes blindness but it also has a profound impact on general morbidity, mortality, and growth., The prevalence of vitamin A deficiency by clinical examination in different parts of India has been estimated to vary from 1.1% to 22.3%.,,,,,, Several studies had identified prevalence of vitamin A deficiency among Indian preschool-aged children. However, the true nature of these findings remains confounded in many studies, producing evidences that were not uniform. To look for sources of potential bias and try to uncover consistent patterns of prevalence, a systematic review on vitamin A deficiency among Indian preschool-aged children was done by an extensive array of data. The main demographic groups of interest for this analysis are Indian preschool-age children. The objective of this study was to determine the baseline data of vitamin A deficiency among Indian preschool-aged children.
Literature search for data sources
We attempted the comprehensive, annotated assembly of survey results by different sources; published surveys, and field studies in which vitamin A deficiency among Indian preschool-aged children were reported, meeting presentations, and personal communications about recent surveys not included in previous analyses. Through an extensive search in indexed literatures and website-based population survey reports, we identified 13 epidemiologic studies of the vitamin A deficiency among Indian preschool-aged children from 250 potentially relevant articles. All published articles in indexed journals available from various institutional libraries of India and websites on epidemiologic studies on vitamin A deficiency among Indian preschool-aged children published between 1960 and 2007 were included in this study. Studies were identified by searching Pubmed-entrez and abstracts from scientific meetings (1985-2007). Review of citations and reference lists was performed to identify additional eligible studies. The search terms included vitamin A deficiency, xerophthalmia, Indian preschool-age children, prevalence. Where possible, sources were contacted for further information on survey data not readily available in the public domain. Manual searches were conducted from review articles and previous meta-analyses. When necessary, we contacted authors for additional information or for translations from languages other than English.
Few criteria were developed to select studies from among peer-reviewed articles. Firstly, a broad criterion of vitamin A deficiency was developed on information provided in the WHO publication by the global experts prior to the study for ensuring feasibility, acceptability, and reliability. Secondly, ‘night blindness (XN)’ among preschool-age children along with corneal xerosis associated with Bitot’s spot(X1B) had been considered as positive clinical signs of vitamin A deficiency disorders during calculations of prevalence rates were sought to included; Studies that did not meet these criteria were rejected. Finally, in the absence of universally accepted criteria of reporting of prevalence by researchers, weighted average data had been considered as positive cases during calculations of prevalence rates irrespective of criteria of diagnosis.
Main outcome variables
Prevalence of vitamin A deficiency among Indian preschool-aged children
We managed data using Microsoft Office Excel 2000 (Microsoft, Redmond, WA) and analyzed the data using SPSS (version 10.0) for windows to calculate median and inter-quartile range.
Data abstraction and synthesis
Wide differences in samples and primary outcome variables in these studies were observed. To be more precise, heterogeneity varied from rural-urban samples to criteria for positive diagnosis. Thereby, results varied to a large extent regarding overall prevalence in a majority of studies. After adjusting for these confounding characteristics, consistent patterns of vitamin A deficiency among Indian preschool-aged children were not found.
Details of the study reports on prevalence of vitamin A deficiency among Indian preschool-aged children were reviewed along with their estimated prevalence rates of vitamin A deficiency disorders in Indian preschool-age children that are tabulated in [Table 1].
The total number of children screened for Vitamin A deficiency disorders in this study population was 208,379 (with median = 1094 and IQR = 283.0 – 8978.0) and the number of preschool-age children suffering from vitamin A deficiency disorders was determined to be of 12,510 (with median = 80 and IQR = 36.5 – 201.0).
With this background information, the median prevalence of vitamin A deficiency disorders in Indian preschool-age children was determined to be 7.0% and inter-quartile range (IQR) = 3.3-9.3%. This implies that there were ~1.7 million vitamin A-deficient preschool-age children in India. Though the study period varied between 1960 and 2007, the median study period was found to be 1999 (with IQR = 1981.5-2004.5).
Wide inter-regional variation in prevalence of vitamin A deficiency among Indian preschool-aged children was observed.
The main demographic groups at risk of vitamin A deficiency disorder and of interest for this analysis are preschool-age children (i.e., <5 years of age). WHO classification has stated that conjunctival xerosis (X1A) is not recommended for community diagnosis. , So conjunctival xerosis (X1A), only when accompanied by Bitot’s spots (X1B), had been included as positive findings.  Other Indian researchers in this age group got higher prevalence. , Sub-clinical deficiencies had been found quite above this level. 
In the study at Bihar, the prevalence of night blindness (XN), Bitot’s spots (X1B) was 1.35 and 2.71%, respectively. A total of 27(0.64%) preschool-age children had both night blindness and Bitot’s spots. Vitamin A deficiency was absent in infants and increased gradually as the age increased; maximum prone and most vulnerable for night blindness and Bitot’s spot as well as xerophthalmia was in the above 3-year age group significantly. This higher age group vulnerability among preschool-age children was in conformity with findings of other investigators. ,,,[22 ] The reason may be suggested that vitamin A requirement is relatively fulfilled by prolonged breast-feeding practice in Indian sub-continent leading to replenishment of hepatic storage of vitamin A breast-feeding may have sufficient prophylactic effect for vitamin A deficiency for preschool-age children upto age 2 years. ,
In sex distribution, there was male preponderance in few studies. The reason for this male preponderance was relatively obscure. In case of night blindness, it may be explained as follows: Indian parents are more conscious for health of male children than female counterparts. They may have missed this observation in female children. Similar observations were found in studies done in other parts of world. ,,
Our summary from studies of vitamin A deficiency among Indian preschool-aged children was that these prevalence studies lack consistency, possibly because of the non-uniform adherence to the diagnostic criteria. Vitamin A deficiency affects large numbers of preschool-aged children in India. This new finding indicates that prevalence of vitamin A deficiency among Indian preschool-aged children in India had been on the decline at a faster rate than previously understood. Due to the lack of nationally representative data on the prevalence, risk factors, and prognosis of the disease, there is an urgent need of more public health research in this field of priority attention and direction.
Source of Support: None, Conflict of Interest: None